P43 is a newly discovered gene of unknown function that is induced by homocysteine in cultured human umbilical vein endothelial cells (HUVEC) and also by nickel in a variety of human cell types including HUVEC. In the long term, research on this gene's function may elucidate mechanisms involved in nickel's essentiality or toxicity (e.g. carcinogenesis). In addition, high plasma homocysteine levels are associated with arteriosclerosis in humans and this disease in rats has been observed following nickel administration. Studies of the induction of P43 by nickel and homocysteine may increase our understanding of the pathogenesis of this disorder. The short term goals are to understand the functions of the P43 gene product and how nickel induces the gene in cultured cells. The specific aims are to (1) determine the effects of under or overexpression of P43 on cellular functions by using antisense or a strong promoter to alter transcription rates of P43 and monitoring induction by Northern blot analysis, immunocytochemistry to study cellular distribution of the P43 protein, and HPLC and TLC to examine intracellular homocysteine metabolism; (2) study the effects of nickel or homocysteine doses on cellular homocysteine metabolism in normal and transformed cells and the biochemical effects of nickel upon homocysteine metabolism via enzymatic assays of methionine.